An apparatus for processing a signal output by an encoder, including a frequency multiplication unit to repeatedly multiply each of frequencies of two sinusoidal signals with a phase difference of approximately 90 degrees by a predetermined number a predetermined number of times; a converter to convert each pair of the two frequency-multiplied sinusoidal signals into square wave signals; and a processor to receive the square wave signals and count a number of rising and/or falling edges of the square wave signals in order to determine and control a position of an object to be controlled.
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17. A method of processing a signal output by an encoder, each signal comprising a first and second sinusoidal signal formed as a pair, the method comprising:
repeatedly multiplying a frequency of the first and second sinusoidal signals, having a phase difference of approximately 90 degrees, by a predetermined number a predetermined number of times, to form pair of two frequency multiplied sinusoidal signals;
converting each pair of the two frequency multiplied sinusoidal signals into square wave signals; and
applying the square wave signals to a processor for determining a position of an object to be controlled according to a number of rising and/or falling edges of the square wave signals, wherein the processor outputs a signal from the encoder.
1. An apparatus for processing a signal output by an encoder, each signal comprising a first and second sinusoidal signal formed as a pair, the apparatus comprising:
a frequency multiplication unit to repeatedly multiply frequency of the first and second sinusoidal signals, the first and second sinusoidal signals having a phase difference of approximately 90 degrees, by a predetermined number a predetermined number of times, into pairs of frequency multiplied sinusoidal signals;
a converter to convert each pair of frequency multiplied sinusoidal signals into square wave signals; and
a processor to receive the square wave signals and count a number of rising and/or falling edges of the square wave signals in order to determine and control a position of an object to be controlled.
14. A speed controlling system including an encoder, the system comprising:
a frequency multiplication unit repeatedly performing an operation n times by which a frequency of a first and second sinusoidal signals is multiplied by 2 to form n pairs of freguency-multiplied sinusoidal signals, wherein the first and second sinusoidal signals are provided by the encoder and the second sinusoidal signal is approximately 90 degrees out of phase with the first sinusoidal signal;
an analog-to-digital converter selecting one pair of the n pairs of frequency-multiplied sinusoidal signals obtained by the frequency multiplication unit according to a control signal and converting the selected pair of frequency-multiplied sinusoidal signals into square wave signals; and
a controller controlling a speed of a to-be-controlled object by counting pulses of square wave signals provided by the analog-to-digital converter.
10. A position controlling system including an encoder, the system comprising:
a frequency multiplication unit repeatedly performing an operation n times by which a frequency of each of a pair of first and second sinusoidal signals is multiplied by 2 to form n pair of frequency-multiplied sinusoidal signals, wherein the first and second sinusoidal signals are provided by the encoder as a pair and the second sinusoidal signal is substantially 90 degrees out of phase with the first sinusoidal signal;
an analog-to-digital converter selecting one pair of the n pairs of frequency-multiplied sinusoidal signals obtained by the frequency multiplication unit according to a control signal and converting the selected pair of frequency-multiplied sinusoidal signals into square wave signals; and
a controller controlling a position of a to-be-controlled object by counting pulses of square wave signals provided by the analog-to-digital converter.
25. A computer readable recording medium that stores a program sequence for executing a method of processing a signal output by an encoder, each signal comprising two sinusoidal signals formed as a pair, the method comprising:
repeatedly multiplying a frequency of two sinusoidal signals having a phase difference of approximately 90 degrees by a predetermined number a predetermined number of times, to form pair of two frequency multiplied sinusoidal signals;
converting each of the predetermined number of pairs of the two frequency multiplied sinusoidal signals into square wave signals; and
applying the square wave signals to a processor for determining a position of an object to be controlled according to a number of rising and/or falling edges of the square wave signals, wherein the processor outputs a signal from the encoder,
wherein the predetermined number that is multiplied to each of the frequency of the two sinusoidal signals is 2 and each of the frequencies of the two sinusoidal signals is repeatedly multiplied by 2 at least once.
2. The apparatus for processing the signal output by the encoder as claimed in
3. The apparatus for processing the signal output by the encoder as claimed in
4. The apparatus as claimed in
5. The apparatus as claimed in
first through n-th frequency multipliers for repeatedly performing an operation by which the frequency of the first and second sinusoidal signals is multiplied by 2, n times.
6. The apparatus as claimed in
a first multiplier multiplying the first and second sinusoidal signals frequency-multiplied by 20 through 2n−1, by 2, to produce the first sinusoidal signal frequency-multiplied by 21 through 2n;
a second multiplier multiplying the first sinusoidal signal frequency-multiplied by 20 through 2n−1, by itself;
a third multiplier multiplying the second sinusoidal signal frequency-multiplied by 20 through 2n−1, by itself; and
a subtractor subtracting an output signal of the second multiplier from an output signal of the third multiplier to produce the second sinusoidal signal frequency-multiplied by 21 through 2n.
7. The apparatus as claimed in
a first comparator receiving the first sinusoidal signal frequency-multiplied by 21 through 2n provided from the frequency multiplication unity comparing the first sinusoidal signal frequency-multiplied by 21 through 2n with a first reference value, and generating a first square wave signal; and
a second comparator receiving the second sinusoidal signal frequency-multiplied by 21 through 2n provided from the frequency multiplication unit, comparing the second sinusoidal signal frequency-multiplied by 21 through 2n with a second reference value, and generating a second square wave signal.
8. The apparatus as claimed in
9. The apparatus as claimed in
a first filter removing unnecessary signals from the first square wave signal received from the first comparator; and
a second filter removing unnecessary signals from the second square wave signal received from the second comparator.
11. The position controlling system as claimed in
first through n-th frequency multipliers for repeatedly performing an operation by which each of the frequencies of the first and second sinusoidal signals is multiplied by 2, n times,
wherein each of the first through n-th frequency multipliers comprises:
a first multiplier multiplying the first and second sinusoidal signals frequency-multiplied by 20 through 2n−1, by 2, to produce the first sinusoidal signal frequency-multiplied by 21through 2n;
a second multiplier multiplying the first sinusoidal signal frequency-multiplied by 20 through 2n−1, by itself;
a third multiplier multiplying the second sinusoidal signal frequency-multiplied by 20 through 2n−1, by itself; and
a subtractor subtracting an output signal of the second multiplier from an output signal of the third multiplier to produce the second sinusoidal signal frequency-multiplied by 21 through 2n.
12. The position controlling system as claimed in
a first comparator receiving the first sinusoidal signal frequency-multiplied by 21 through 2n provided from the frequency multiplication unit, comparing the first sinusoidal signal frequency-multiplied by 21 through 2n with a first reference value, and generating a first square wave signal; and
a second comparator receiving the second sinusoidal signal frequency-multiplied by 21 through 2n provided from the frequency multiplication unit, comparing the second sinusoidal signal frequency-multiplied by 21 through 2n with a second reference value, and generating a second square wave signal.
13. The position controlling system as claimed in
15. The speed controlling system as claimed in
first through n-th frequency multipliers for repeatedly performing an operation by which the frequency of the first and second sinusoidal signals is multiplied by 2, n times,
wherein each of the first through n-th frequency multipliers comprises:
a first multiplier multiplying the first and second sinusoidal signals frequency-multiplied by 20 through 2n−1, by 2, to produce the first sinusoidal signal frequency-multiplied by 21 through 2n;
a second multiplier multiplying the first sinusoidal signal frequency-multiplied by 20 through 2n−1, by itself;
a third multiplier multiplying the second sinusoidal signal frequency-multiplied by 20 through 2n−1, by itself; and
a subtractor subtracting an output signal of the second multiplier from an output signal of the third multiplier to produce the second sinusoidal signal frequency-multiplied by 21 through 2n.
16. The speed controlling system as claimed in
a first comparator receiving the first sinusoidal signal frequency-multiplied by 21 through 2n provided from the frequency multiplication unit, comparing the first sinusoidal signal frequency-multiplied by 21 through 2n with a first reference value, and generating a first square wave signal; and
a second comparator receiving the second sinusoidal signal frequency-multiplied by 21 through 2n provided from the frequency multiplication unit, comparing the second sinusoidal signal frequency-multiplied by 21 through 2n with a second reference value, and generating a second square wave signal.
18. The signal processing method of the encoder as claimed in
19. The signal processing method of the encoder as claimed in
20. The method of processing the signal output by the encoder as claimed in
multiplying the first and second sinusoidal signals frequency-multiplied by 20 through 2n−1, by 2, to produce the first sinusoidal signal frequency-multiplied by 21 through 2n;
multiplying the first sinusoidal signal frequency-multiplied by 20 through 2n−1, by itself;
multiplying the second sinusoidal signal frequency-multiplied by 20 through 2n−1, by itself; and
subtracting the results obtained by multiplying the second sinusoidal signal frequency-multiplied by 20 through 2n−1, by itself from the results obtained by multiplying the first sinusoidal signal frequency-multiplied by 20 through 2n−1, by itself, to produce the second sinusoidal signal frequency-multiplied by 21 through 2n.
21. The method of processing the signal output by the encoder as claimed in
receiving the first sinusoidal signal frequency-multiplied by 21 through 2n, comparing the first sinusoidal signal frequency-multiplied by 21 through 2n with a first reference value, and generating a first square wave signal; and
receiving the second sinusoidal signal frequency-multiplied by 21 through 2n, comparing the second sinusoidal signal frequency-multiplied by 21 through 2n with a second reference value, and generating a second square wave signal.
22. The signal processing method of the encoder as claimed in
23. The signal processing method of the encoder as claimed in
24. The signal processing method of the encoder as claimed in
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This application claims the priority of Korean Patent Application No. 2003-48648, filed on Jul. 16, 2003, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The invention relates to a motor control, and more particularly, to a signal processing method and apparatus for improving the speed and the position resolutions of an encoder output signal when the motor control is performed using an analog output encoder.
2. Description of the Related Art
In conventional ink jet imaging apparatuses, a recording medium is carried therein using at least one feed roll along a carry path. To form an image accurately on the recording medium, the recording medium must be placed at a specific location. To position the recording medium at the specific location, the feed roll must move with high precision. Hence, the quality of an image is often very dependent upon precise control of the position of the feed roll. An encoder is typically used to precisely control the position of a feed roll.
An encoder typically uses at least one sensor to sense slits that are position marks and formed along the track of a code wheel, for example, a disk. Preferably, the code wheel has a central shaft in alignment with the central shaft of a feed roll and rotates with a rotation of the feed roll. When the code wheel rotates, the number of slits by which the sensor and its accompanying elements pass is counted. Since each of the slits indicates movement of the code wheel at a predetermined angle, changes in the position of the recording medium carried by the feed roll can be tracked.
A square-wave pulse encoder cannot obtain distinct position information between rising and falling edges of a square-wave pulse output by the encoder. Hence, an analog output encoder is used because fine position information can be obtained even during one cycle by finely dividing the angles of rotation of a motor by analog values. To increase a resolution of an analog output encoder, a code wheel is enlarged, or the interval between adjacent slits is reduced. However, if the code wheel is enlarged, the analog output encoder becomes large and bulky. If the interval between adjacent slits is reduced, an encoder output signal is highly likely to be unstabilized due to the characteristics of the electrical circuit of a sensor, the sensitivity of the sensor, and the mechanical and optical characteristics of the code wheel.
Also, to increase the resolution of an analog output encoder, a signal processing circuit is used, in which a sinusoidal signal output by the analog output encoder is divided into 2n sections according to the resolution of analog-to-digital conversion, that is, according to the number of bits, n, and an instantaneous value is read out from each of the 2n sections so that analog-to-digital conversion is performed. However, in this method, numerical errors and jitters often occur on the curve of the sinusoidal signal due to the characteristics of the sinusoidal signal in that only about π/4 of a half-period maintains linearity, and, accordingly, a processor using an analog-to-digital converted signal cannot precisely control the location or speed of a recording medium. Also, because the sections sequentially undergo the analog-to-digital conversion, delay time is generated, and a load on the processor increases. Such problems adversely affect other signal processing operations performed in the processor.
One aspect of the invention provides a method of and an apparatus for processing a signal output by an encoder, in which sinusoidal signals having different phases, which are output by the encoder, are frequency-multiplied, and the frequency-multiplied sinusoidal signals are converted into square-wave signals, and a position controlling system which adopts the signal processing apparatus and method so as to precisely control the position or speed of a to-be-controlled object.
According to an aspect of the invention, there is provided a method of processing a signal output by an encoder, includes: repeatedly performing an operation n times (where n is an integer equal to or greater than 1), by which each of frequencies of a pair of first and second sinusoidal signals is multiplied by 2, wherein the first and second sinusoidal signals are provided by the encoder and the second sinusoidal signal is substantially 90 degrees out of phase with the first sinusoidal signal; selecting one pair of n pairs of frequency-multiplied sinusoidal signals in response to a control signal and converting the selected frequency-multiplied sinusoidal signal pair into square wave signals.
According to another aspect of the invention, there is provided an apparatus for processing a signal output by an encoder, including a frequency multiplication unit repeatedly performing an operation n times (where n is an integer equal to or greater than 1), by which each of frequencies of a pair of first and second sinusoidal signals is multiplied by 2, wherein the first and second sinusoidal signals are provided by the encoder and the second sinusoidal signal is substantially 90 degrees out of phase with the first sinusoidal signal; and an analog-to-digital converter converting each of n pairs of frequency-multiplied sinusoidal signals obtained by the frequency multiplication unit into square wave signals
According to an aspect of the invention, there is provided a position or speed controlling system including: a frequency multiplication unit repeatedly performing an operation n times (where n is an integer equal to or greater than 1), by which each of frequencies of a pair of first and second sinusoidal signals is multiplied by 2, wherein the first and second sinusoidal signals are provided by the encoder and the second sinusoidal signal is substantially 90 degrees out of phase with the first sinusoidal signal; an analog-to-digital converter selecting one pair of the n pairs of frequency-multiplied sinusoidal signals obtained by the frequency multiplication unit in response to a control signal and converting the selected frequency-multiplied sinusoidal signal pair into square wave signals; and a controller controlling the position or speed of a to-be-controlled object by counting pulses of square wave signals provided by the analog-to-digital converter.
Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
Reference will now be made in detail to the embodiments of the invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below to explain the invention by referring to the figures.
Referring to
The encoder signal receiver 210 receives an A phase sinusoidal signal A1 and a B phase sinusoidal signal B1 from the encoder 100 of
The ADC 230 receives the sinusoidal signals A2 and B2 from the frequency multiplier 220 and performs an analog-to-digital conversion on each sinusoidal signal to generate square wave signals A3 and B3.
The controller 240 receives the square wave signals A3 and B3 from the ADC 230, counts the number of rising and/or falling edges, that is, pulses of the square wave signals A3 and B3, to determine the current position or speed of a to-be-controlled object, and feeds the determined position or speed value back to the encoder 100.
The frequency multiplier 220, the ADC 230, and the controller 240 may be integrated as one chip using an Application Specific Integrated Circuit (ASIC).
The detailed structures of the frequency multiplier 220 and the ADC 230 are described in detail below with reference to
As shown in
The first multiplier 310 multiplies the frequencies of the A-phase and B-phase sinusoidal signals A1 and B1 shown in
A2=2(A1)(B1)=2 sin(φ)(−cos φ)=−sin(2 φ) (1)
The second multiplier 320 multiplies the frequency of the A-phase sinusoidal signal A1 shown in
The subtractor 340 subtracts the output of the second multiplier 320 from that of the output of the third multiplier 330 to generate the sinusoidal signal B2 shown in
B2=cos(φ)2−sin(φ)2=cos(2φ) (2)
The sinusoidal signals A2 and B2 output by the first multiplier 310 and the subtractor 340, respectively, have half of the periods of and the same amplitudes as the sinusoidal signals A1 and B1 received from the encoder signal receiver 210. In other words, the sinusoidal signals A2 and B2 have frequencies that are double the frequencies of the sinusoidal signals A1 and B1.
The second comparator 420 compares the sinusoidal signal B2 received from the frequency multiplier 220 with a second reference value (e.g., 0), which is a value half way between the maximum amplitude (e.g., +1) and minimum amplitude (e.g., −1) of the sinusoidal signal B2 in order to produce, for example, a digital signal with a duty of 50%. The second comparator 420 outputs a “+1” signal when the sinusoidal signal B2 is greater than the second reference value, and a “−1” signal when the sinusoidal signal B2 is smaller than the second reference value, thereby generating the square wave signal B3 as shown in
The first filter 430 receives the square wave signal A3 from the first comparator 410 and filters the same to remove an unnecessary signal, such as noise, included in it. The second filter 440 receives the square wave signal B3 from the second comparator 420 and filters the same to remove an unnecessary signal, such as, noise, included in it.
Each of the first through n-th frequency multipliers 611, 612, and 613 has the same structure as that of the frequency multiplier 220 of
The selector 620 selects one pair of the frequency-multiplied sinusoidal signals received from the frequency multiplication unit 610 in response to a control signal and provides the selected sinusoidal signal pair to the ADC 630. The control signal is produced in various ways. If the control signal includes k bits, one pair can be selected from 2k pairs of frequency-multiplied sinusoidal signals obtained by the frequency multiplication unit 610. At this time, one pair of sinusoidal signals may be selected among the 2k pairs of frequency-multiplied sinusoidal signals obtained by the frequency multiplication unit 610, in proportion with precise control of the location or speed of an object to-be-controlled using the output signal of the encoder 100. In an aspect, when the control signal includes 2 bits and the control of the location or speed of an object to-be-controlled requires a high precision, 24 frequency-multiplied sinusoidal signals may be selected from 22 (=4) pairs of frequency-multiplied sinusoidal signals, that is, 21 through 24 frequency-multiplied sinusoidal signals obtained by the frequency multiplication unit 610.
The ADC 630 has the same structure as the ADC 230 shown in
In operation 720, an operation by which each of frequencies of the two sinusoidal signals A1 and B1 is multiplied by a predetermined integer, such as 2, is repeatedly performed n times, on the basis of the maximum multiplier, 2n, for the sinusoidal signals A1 and B1.
In operation 730, one pair is selected from n pairs of sinusoidal signals, that is, 21 through 2n frequency-multiplied sinusoidal signals obtained by multiplying frequencies of the sinusoidal signals A1 and B1 by 21 through 2n. In operation 740, the selected frequency-multiplied sinusoidal signals are converted into square wave signals. In operation 750, the square wave signals are filtered and provided to the controller 240 of
However, if the encoder signal processing method according to the invention does not include operation 730, an operation by which each of frequencies of the two sinusoidal signals A1 and B1 is multiplied by a predetermined integer, such as 2, is repeatedly performed n times, on the basis of the determined maximum multiplier, n. Thereafter, in operations 740 and 750, final 2n frequency-multiplied sinusoidal signals are converted into square wave signals, and the square wave signals are filtered.
In other words, a process in which an operation by which each of frequencies of the sinusoidal signals A1 and B1 are multiplied by 2 is repeatedly performed n times, and final 2n frequency-multiplied sinusoidal signals are converted into square wave signals according to the invention, corresponds to a general n-bit analog-to-digital conversion. To be more specific, an 8-bit analog-to-digital conversion corresponds to a process in which 28 frequency-multiplied sinusoidal signals are converted into square wave signals according to the invention, but the process according to the invention provides a much higher precision, i.e., resolution.
The invention can be embodied as computer readable codes on a computer readable recording medium to be read by a computer. The computer readable recording medium is any data storage device that can store data that can be thereafter read by a computer system. Examples of the computer readable recording medium include read-only memory (ROM), random-access memory (RAM), CD-ROMs, magnetic tapes, floppy disks, optical data storage devices, and so on. Also, the computer readable codes can be transmitted via a carrier wave such as Internet. The computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion. Functional programs, codes, and code segments for accomplishing the invention can be easily construed by programmers in the technical field to which the invention pertains.
In the invention, as described above, an operation by which each of frequencies of two sinusoidal signals with a phase difference of about 90 degrees provided by an encoder are multiplied by a predetermined integer, such as 2, is repeatedly performed n times, and 2n frequency-multiplied sinusoidal signals are converted into square wave signals. The square wave signals are applied to a controller for controlling the location or speed of a to-be-controlled object by using an output signal of the encoder. As a result, it is not necessary to read out 2n instantaneous values for sinusoidal signals output by the encoder according to a resolution (n bits) for an analog-to-digital conversion. Therefore, the load upon the processor is reduced.
Further, the encoder signal processing method and apparatus according to the invention can be applied to various types of encoders, such as, a rotary encoder used to detect the rotation angle of a disk attached to a rotating shaft for carrying a print medium of a printer, or a linear encoder used to detect the moving distance of a print head that moves linearly. Thus, the physical resolution of the encoder can be improved without increasing the number of slits arranged on the disk.
In addition, the encoder signal processing method and apparatus according to the invention can be applied to various types of systems for controlling the location or speed of a to-be-controlled object by using an output signal of the encoder. Thus, the physical resolution of the encoder can be improved without increasing the number of slits arranged on the disk.
Further, because the number of slits arranged on the disk can be reduced according to the invention, it is possible to reduce the radius of the disk of the encoder. Thus, the overall size of the encoder can be reduced, thereby reducing the costs for manufacturing the encoder.
Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.
Kang, Kyung-pyo, Kim, Hyoung-It
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